Sensing element and optical distance measurement system

ABSTRACT

A sensing element includes a plurality of sensing pixel areas arranged in matrix, wherein each of the plurality of sensing pixel areas includes a first pixel, a second pixel, a first shielding layer, a second shielding layer and at least one micro lens. The second pixel is adjacent to the first pixel in a predetermined direction. The first shielding layer is disposed on the first pixel and has a first opening, wherein an aperture of the first opening increases along the predetermined direction from a center of the first pixel. The second shielding layer is disposed on the second pixel and has a second opening, wherein a shape of the second opening is mirror symmetrical with that of the first opening in the predetermined direction. The at least one micro lens is disposed on the first shielding layer and the second shielding layer.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 15/080,679, filed on Mar. 25, 2016, which claims the prioritybenefit of Taiwan Patent Application Ser. No. 104112987, filed on Apr.22, 2015, the full disclosure of which is incorporated herein byreference.

BACKGROUND 1. Field of the Disclosure

This disclosure generally relates to a sensing element, moreparticularly, to a sensing element an optical distance measurementsystem applicable to the distance measurement or the gesturerecognition.

2. Description of the Related Art

In general, a distance measurement system employs a light source andcalculates an object distance according to energy of light beam of thelight source reflected back by the object. Traditionally, it is able touse the triangulation method or time-of-flight (TOF) technique tocalculate the distance. However, these methods require a higher cost anda larger system size.

In addition, the development of gesture recognition generally removesthe background image at first by using a 3D image so as to separate theobject image. In this technique, two image sensors are used such thatthe size and cost of a gesture recognition module can not be effectivelyreduced.

As mentioned above, the present disclosure obtains the 3D image by usingthe phase detection, and an additional illumination light (as used inthe TOF mentioned above) is not necessary. In the proposed technique ofthe present disclosure, a single image sensor is employed to be able toimplement the distance measurement and the gesture recognition.

SUMMARY

Accordingly, the present disclosure provides a sensing element and anoptical distance measurement system with a low cost, small size and highdetection accuracy.

The present disclosure provides a sensing element including a pluralityof sensing pixel areas, wherein each of the sensing pixel areas includesa first pixel, a second pixel, a first shielding layer, a secondshielding layer and at least one micro lens. The second pixel isadjacent to the first pixel. The first shielding layer is disposed uponthe first pixel and has a first opening, wherein an aperture of thefirst opening increases along a predetermined direction from a center ofthe first pixel. The second shielding layer is disposed upon the secondpixel and has a second opening, wherein a shape of the second opening ismirror symmetrical to that of the first opening along the predetermineddirection. The at least one micro lens is disposed upon the firstshielding layer and the second shield layer, wherein the first pixel andthe second pixel respectively receive incident light beams of differentphases.

The present disclosure further provides an optical distance measurementsystem including a lens, a sensing element and a processing unit. Thesensing element senses light penetrating the lens and outputs an imageframe, and includes a plurality of sensing pixel areas, wherein each ofthe sensing pixel areas includes a first pixel, a second pixel, a firstshielding layer, a second shielding layer and at least one micro lens.The first shielding layer is disposed upon the first pixel and having afirst opening, wherein an aperture of the first opening increases alonga first direction from a center of the first pixel. The second shieldinglayer is disposed upon the second pixel and having a second opening,wherein an aperture of the second opening increases along an inversedirection of the first direction from a center of the second pixel. Theat least one micro lens is disposed between the lens and the firstshielding layer as well as the second shielding layer. The processingunit generates, according to the image frame, a first subframecorresponding to the first pixels and a second subframe corresponding tothe second pixels, and estimates a plurality of distances of differentpositions, according to the first subframe and the second subframe, on asurface of an object to obtain a three-dimensional image of the object.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, advantages, and novel features of the present disclosurewill become more apparent from the following detailed description whentaken in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram of an optical distance measurement systemaccording to a first embodiment of the present disclosure.

FIG. 2A is a top view of a sensing element of the optical distancemeasurement system of FIG. 1.

FIG. 2B is a partially enlarged view of FIG. 2A.

FIG. 3 is a schematic diagram of a sensing element of an opticaldistance measurement system according to one embodiment of the presentdisclosure.

FIG. 4 is a schematic diagram of estimating an object distance accordingto an image frame by a processing unit according to a first embodimentof the present disclosure.

FIG. 5A is a top view of a sensing element of an optical distancemeasurement system according a second embodiment of the presentdisclosure.

FIG. 5B is a schematic diagram of estimating an object distanceaccording to an image frame by a processing unit according to a secondembodiment of the present disclosure.

FIGS. 6A-8B are schematic diagrams of sensing pixel areas havingopenings of different shapes.

FIG. 9 is a top view of a sensing element of an optical distancemeasurement system according a third embodiment of the presentdisclosure.

DETAILED DESCRIPTION OF THE EMBODIMENT

It should be noted that, wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Referring to FIG. 1, it is a schematic diagram of an optical distancemeasurement system 1 according to a first embodiment of the presentdisclosure. The optical distance measurement system 1 includes a lens10, a sensing element 12 and a processing unit 14. In this embodiment,the optical distance measurement system 1 is used to estimate at leastone object distance. For example, when an object 9 enters a validdetection range of the optical distance measurement system 1, theoptical distance measurement system 1 estimates at least one distance ofthe object 9 with respect to the optical distance measurement system 1(described later).

It should be mentioned that FIG. 1 shows only one object (e.g. theobject 9) for illustrating the present disclosure, but not limitedthereto. In some embodiments, the distance of each of a plurality ofobjects within the valid detection range of the optical distancemeasurement system 1 is able to be estimated. In some embodiments, theobject 9 has a rough surface, and the optical distance measurementsystem 1 estimates a plurality of distances, with respect to the opticaldistance measurement system 1, of different positions on the roughsurface of the object 9 to obtain three-dimensional image information.

The lens 10 is used to condense light, e.g., reflected light from theobject 9. The lens 10 is separated, e.g., via a spacer, but not limitedto, from the sensing element 12 by a fixed distance. In otherembodiments, the lens 10 keeps the fixed distance from the sensingelement 12 by a casing or a supporting member. In addition, althoughFIG. 1 shows one lens 10, the present disclosure is not limited thereto.In other embodiments, the lens 10 is a lens set including a plurality oflenses.

The sensing element 12 is used to capture light penetrating the lens 10and output an image frame IF. The sensing element 12 is, e.g., a chargecoupled device (CCD) image sensor, a complementary metal oxidesemiconductor (CMOS) image sensor or other sensors for sensing lightenergy. The sensing element 12 includes a plurality of sensing pixelareas As arranged in a matrix, wherein each of the sensing pixel areasAs includes a first pixel P₁, a second pixel P₂, a first shielding layerS₁, a second shielding layer S₂ and at least one micro lens L_(M).

Referring to FIGS. 1, 2A and 2B, every component of each of the sensingpixel areas As is illustrated hereinafter. FIG. 2A is a top view of thesensing element 12 of FIG. 1, wherein the at least one micro lens L_(M)is not shown in FIG. 2A. As shown in FIG. 2A, the second pixel P₂ isadjacent to the first pixel P₁ in a predetermined direction (e.g. an xdirection) in this embodiment. In addition, in this embodiment, a shapeof the first pixel P₁ and the second pixel P₂ is shown as a square, butnot limited thereto. In other embodiments, a shape of the first pixel P₁and the second pixel P₂ is a circle or a rectangle. Although FIG. 2Ashows that the sensing element 12 has 6×5 sensing pixel areas As, butthe present disclosure is not limited thereto. A number of the sensingpixel areas As is determined according to actual applications.

FIG. 2B is a partial enlarged view of FIG. 2A, and in FIG. 2B onesensing pixel area As is shown. The first shielding layer S₁ is disposedupon the first pixel P₁ and has a first opening O₁, wherein an apertureof the first opening O₁ increases or monotonically increases along thepredetermined direction from a center of the first pixel P₁. The secondshielding layer S₂ is disposed upon the second pixel P₂ and has a secondopening O₂, wherein a shape of the second opening O₂ is mirrorsymmetrical to that of the first opening O₁ along the predetermineddirection (e.g. the X direction). That is, an aperture of the secondopening O₂ increases along an inverse direction of the predetermineddirection from a center of the second pixel P₂. It should be mentionedthat the first shielding layer S₁ and the second shielding layer S₂ areused to block a part of light penetrating the micro lens L_(M). Theother part of light not being blocked propagates through the firstopening O₁ of the first shielding layer S₁ and the second opening O₂ ofthe second shielding layer S₂ and reaches the first pixel P₁ and thesecond pixel P₂.

It is appreciated that, in FIG. 2B, a first area summation of the firstshielding layer S₁ and the first opening O₁ is equal to an area of thefirst pixel P₁, and a second area summation of the second shieldinglayer S₂ and the second opening O₂ is equal to an area of the secondpixel P₂, but not limited to. In other embodiments, the first areasummation is a little larger than the area of the first pixel P₁ and thesecond area summation is a little larger than the area of the secondpixel P₂ to avoid light leakage.

The first shielding layer S₁ and the second shielding layer S₂ areselected from two layers of the first metal layer to the tenth metallayer in the CMOS manufacturing process, or made of other lightshielding material.

In one embodiment, after the first shielding layer S₁ and the secondshielding layer S₂ are formed, e.g., made of metal material, anisolation layer or a passivation layer is optionally covered on thefirst shielding layer S₁ and the second shielding layer S₂. In thiscase, the isolation layer or the passivation layer is preferably made oflight transmissive material such that the first opening O₁ and thesecond opening O₂ have a high light transmission rate. It is appreciatedthat the isolation layer or the passivation layer is able to preventdust from entering the first pixel P₁ and the second pixel P₂ to degradethe light sensitivity.

In this embodiment, although FIG. 1 shows that the first shielding layerS₁ and the second shielding layer S₂ are separated from the first pixelP₁ and the second pixel P₂ by a distance (e.g. via the isolation layeror the passivation layer), the first shielding layer S₁ and the secondshielding layer S₂ are preferably close to the first pixel P₁ and thesecond pixel P₂ as much as possible. In other embodiments, the firstshielding layer S₁ and the second shielding layer S₂ are directly coatedon or laid over the first pixel P₁ and the second pixel P₂,respectively.

The at least one micro lens L_(M) is disposed between the lens 10 andthe first shielding layer S₁ as well as the second shielding layer S₂.As shown in FIG. 1, for example each of the sensing pixel areas Asincludes two micro lenses L_(M), and the two micro lenses L_(M) arerespectively aligned with the first pixel P₁ and the second pixel P₂. Inthis case, through the arrangement of the two micro lenses L_(M) as wellas the first opening O₁ and the second opening O₂ being mirrorsymmetrical to each other, the first pixel P₁ and the second pixel P₂respectively receive incident light beams of different phases for thephase detection.

It should be mentioned that through the above arrangement of the microlens and the opening, when the first pixel P₁ and the second pixel P₂receives incident light beams, received incident light closing to acenter of the first pixel P₁ and received incident light closing to acenter of the second pixel P₂ do not have an obvious phase differencefrom each other. On the contrary, received incident light closing to anedge (e.g. a right edge in FIG. 2B) of the first pixel P₁ and receivedincident light closing to an edge (e.g. a left edge in FIG. 2B) of thesecond pixel P₂ have a larger phase difference from each other.Therefore, corresponding to the first opening O₁, the aperture of thefirst opening O₁ closing to the edge of the first pixel P₁ is preferablylarger than the aperture of the first opening O₁ closing to the centerof the first pixel P₁. That is, the aperture of the first opening O₁increases along the predetermined direction from the center of the firstpixel P₁. In this way, the accuracy of phase detection is increased.

It is appreciated that as the aperture of the first opening O₁ increasesalong the predetermined direction from the center of the first pixel P₁,an area of the first opening O₁ is smaller than a half area of the firstpixel P₁, as shown in FIG. 2B. Meanwhile, areas of the first opening O₁and the second opening O₂ are larger than a predetermined area such thatthe image frame IF captured by the sensing element 12 has an acceptablesignal to noise ratio (SNR). Preferably, an area of the first opening O₁is 5 to 45 percent of an area of the first pixel P₁.

As the micro lens L_(M) has a symmetrical structure, in otherembodiments each of the sensing pixel areas As includes only one microlens L_(M). In this case, the one micro lens L_(M) is aligned with bothof the first opening O₁ and the second opening O₂, as shown in FIG. 3.In addition, a passivation layer is optionally formed between the microlenses L_(M) and the shielding layers.

Referring to FIGS. 1, 2A and 4, FIG. 4 is a schematic diagram ofestimating an object distance according to an image frame IF by aprocessing unit 14. The processing unit 14 is, e.g., a digital signalprocessor (DSP) or a processing circuit, and electrically coupled to thesensing element 12. After the sensing element 12 outputs the image frameIF (e.g. corresponding to the 6×10 pixel matrix shown in FIG. 2A) to theprocessing unit 14, the processing unit 14 generates, according to theimage frame IF, a first subframe F₁ corresponding to the first pixels P₁and a second subframe F₂ corresponding to the second pixels P₂. Forexample, when the image frame IF corresponds to the 6×5 sensing pixelareas As of the sensing element 12 (i.e. the 6×10 pixel matrix) of FIG.2A, gray level information of the 6×5 first pixels P₁ and the 6×5 secondpixels P₂ are used to form the first subframe F₁ and the second subframeF₂, respectively.

Generally, when the object 9 is in focus with respect to the opticaldistance measurement system 1, a clear object image appears in the imageframe IF captured by the sensing element 12. Meanwhile, correspondingimaging positions of the object 9 in the first subframe F₁ and in thesecond subframe F₂ generated according to the image frame IF aresubstantially identical. That is, when the imaging positions of theobject 9 respectively present in the first subframe F₁ and the secondsubframe F₂ are overlapped (e.g. a distance therebetween is 0), a lineardistance between the object 9 and the optical distance measurementsystem 1 is defined as a reference distance L0 herein.

However, when the object 9 is out of focus with respect to the opticaldistance measurement system 1, two object images are present in theimage frame IF captured by the sensing element 12, and the two objectimages are at a first imaging position I₁ in the first subframe F₁ andat a second imaging position I₂ in the second subframe F₂, as shown inFIG. 4. In this case, for example a center line in the first subframe F₁perpendicular to the predetermined direction is defined as a firstreference line R₁ and for example a center line in the second subframeF₂ perpendicular to the predetermined direction is defined as a secondreference line R₂. Then, the processing unit 14 calculates a firstprojective distance D₁ between the first imaging position I₁ and thefirst reference line R₁ and calculates a second projective distance D₂between the second imaging position I₂ and the second reference line R₂.

It should be mentioned that the reference distance L0 is assumed to beknown when the first imaging position I₁ and the second imaging positionI₂ are overlapped, and in this case the first projective distance D₁ andthe second projective distance D₂ are both 0 if the object image is atthe center of the image frame IF. As a distance of the object 9 from theoptical distance measurement system 1 has a predetermined relationship,e.g. a linear or nonlinear relationship, with respect to the firstprojective distance D₁ of the first imaging position I₁ generated by theobject 9 in the first subframe F₁ (or the second projective distance D₂of the second imaging position I₂ generated by the object 9 in thesecond subframe F₂), the optical distance measurement system 1previously stores the reference distance L0 and the predeterminedrelationship in a storage memory. Accordingly, the processing unit 14 isable to estimate at least one object distance (i.e. the distance of theobject 9 from the optical distance measurement system 1) according tothe first imaging position I₁ and the second imaging position I₂.

In one embodiment, the processing unit 14 estimates the at least oneobject distance according to a difference value between the firstprojective distance D₁ and the second projective distance D₂ (e.g.,D₁-D₂). For example, a look-up table, e.g. shown in Table 1 below(wherein the object distance L2>L0>L1), is previously formed accordingto a relationship of the difference value with respect to the distanceof the object 9 from the optical distance measurement system 1 to bepreviously stored in the storage memory.

TABLE 1 first projective second projective difference value distance D₁distance D₂ (D₁ − D₂) object distance 0 0 0 L0 −1 +1 −2 L1 +1 −1 2 L2

In another embodiment, the relationship of the difference value withrespect to the distance between the object 9 and the optical distancemeasurement system 1 is formed as a linear equation mathematically to bepreviously stored in the storage memory, but not limited thereto. Inbrief, the processing unit 14 of the optical distance measurement system1 of this embodiment calculates at least one object distance accordingto the first imaging position I₁ of the first subframe F₁ and the secondimaging position I₂ of the second subframe F₂. Compared with theconventional distance measurement system (DMS) which requires lighting,the lighting is not necessary in the optical distance measurement system1 of this embodiment and the object distance is detectable using a lessnumber of first pixels P₁ and second pixels P₂ such that this embodimenthas the advantages of low cost and small size.

Compared with the first embodiment of the present disclosure in whichthe sensing pixel area As includes two mirror symmetrical pixels (e.g.the first pixel P₁ and the second pixel P₂), the sensing pixel area Asof the second embodiment of the present disclosure includes more thantwo pixels, e.g., including four pixels. Referring to FIGS. 1, 5A and5B, FIG. 5A is a top view of a sensing element according a secondembodiment of the present disclosure, and FIG. 5B is a schematic diagramof estimating an object distance according to an image frame by aprocessing unit according to a second embodiment of the presentdisclosure. An optical distance measurement system 1 of the secondembodiment of the present disclosure includes a lens 10, a sensingelement 12 and a processing unit 14, wherein the function of the lens 10has been described in the first embodiment and thus details thereof arenot repeated herein.

The sensing element 12 is used to sense light penetrating the lens 10and output an image frame (e.g. an image frame IF shown in FIG. 5B, theimage frame IF corresponding to a 8×12 pixel matrix of FIG. 5A). Thesensing element 12 includes a plurality of sensing pixel areas Asarranged in a matrix, wherein each of the sensing pixel areas Asincludes a first pixel P₁, a second pixel P₂, a third pixel P₃ and afourth pixel P₄, as shown in FIG. 5A.

Each of the sensing pixel areas As further includes a first shieldinglayer S₁, a second shielding layer S₂, a third shielding layer S₃ and afourth shielding layer S₄. The first shielding layer S₁ is disposed uponthe first pixel P₁ and has a first opening O₁, wherein an aperture ofthe first opening O₁ increases or monotonically increases along a firstdirection (e.g. an x direction) from a center of the first pixel P₁. Thesecond shielding layer S₂ is disposed upon the second pixel P₂ and has asecond opening O₂, wherein a shape of the second opening O₂ is mirrorsymmetrical to that of the first opening O₁ in the first direction. Thethird shielding layer S₃ is disposed upon the third pixel P₃ and has athird opening O₃, wherein an aperture of the third opening O₃ increasesor monotonically increases along a second direction (e.g. a y direction)from a center of the third pixel P₃. The fourth shielding layer S₄ isdisposed upon the fourth pixel P₄ and has a fourth opening O₄, wherein ashape of the fourth opening O₄ is mirror symmetrical to that of thethird opening O₃ in the second direction.

In this embodiment, the first direction (e.g. the x direction) isperpendicular to the second direction (e.g. the y direction), but notlimited thereto.

Then, four micro lenses (not shown) are respectively disposed betweenthe lens 10 and the first shielding layer S₁, the second shielding layerS₂, the third shielding layer S₃ as well as the fourth shielding layerS₄, e.g., respectively arranged upon the shielding layer S₁ to S₄ andaligned with the first pixel P₁, the second pixel P₂, the third pixel P₃and the fourth pixel P₄, wherein the micro lenses in this embodimenthave the same function as the micro lenses L_(M) of the first embodimentand thus details thereof are not repeated herein.

It should be mentioned that the first opening O₁ and the second openingO₂ of this embodiment respectively have identical shapes and functionsto the first opening O₁ and the second opening O₂ of the firstembodiment. However, different from the first embodiment, the sensingpixel area As of this embodiment further includes the third opening O₃,the fourth opening O₄ and corresponded pixels and shielding layers. Itis appreciated that after the third shielding layer S₃ and the fourthlayer S₄ are counterclockwise rotated about the sensing pixel area As by90 degrees, the rotated third shielding layer S₃ and the rotated fourthshielding layer S₄ respectively have an identical shape to the firstshielding layer S₁ and the second shielding layer S₂. Meanwhile, therotated third opening O₃ and the rotated fourth opening O₄ respectivelyhave an identical shape to the first opening O₁ and the second openingO₂. Accordingly, the third opening O₃ and the fourth opening O₄ have thesame function, in the second direction, as the first opening O₁ and thesecond opening O₂ in the first direction.

Next, in addition to generating a first subframe F₁ corresponding to thefirst pixels P₁ and a second subframe F₂ corresponding to the secondpixels P₂ according to the image frame IF, the processing unit 14further generates a third subframe F₃ corresponding to the third pixelsP₃ and a fourth subframe F₄ corresponding to the fourth pixels P₄according to the image frame IF, and estimates at least two objectdistances according to a first imaging position I₁ of the first subframeF₁, a second imaging position I₂ of the second subframe F₂, a thirdimaging position I₃ of the third subframe F₃ and a fourth imagingposition I₄ of the fourth subframe F₄.

For example, the first subframe F₁ and the second subframe F₂respectively have a center line perpendicular to the first direction(e.g. the x direction) to be defined as a first reference line R₁ and asecond reference line R₂, respectively. The third subframe F₃ and thefourth subframe F₄ respectively have a center line perpendicular to thesecond direction (e.g. the y direction) to be defined as a thirdreference line R₃ and a fourth reference line R₄, respectively. Theprocessing unit 14 then calculates a first projective distance D₁between the first imaging position I₁ and the first reference line R₁,calculates a second projective distance D₂ between the second imagingposition I₂ and the second reference line R₂, calculates a thirdprojective distance D₃ between the third imaging position I₃ and thethird reference line R₃ and calculates a fourth projective distance D₄between the fourth imaging position I₄ and the fourth reference line R₄,and estimates the at least two object distances according to a firstdifference value between the first projective distance D₁ and the secondprojective distance D₂ and according to a second difference valuebetween the third projective distance D₃ and the fourth projectivedistance D₄, wherein the method of the processing unit 14 estimating theobject distance has been described in the first embodiment and FIG. 4,and thus details thereof are not repeated herein.

In addition, as the third shielding layer S₃ and the first shieldinglayer S₁ of the sensing element 12 have an identical shape, a thirdopening O₃ of the third shielding layer S₃ has an identical shape andarea as a first opening O1 of the first shielding layer S₁, e.g., atriangle shown in FIG. 5A, but not limited thereto. In one embodiment,the first opening O₁ and the third opening O₃ have an identical area butdifferent shapes, e.g., the first opening O₁ being a trapezoid and thesecond opening O₂ being a semicircle, and the trapezoid and thesemicircle have an identical area.

In the embodiment of the present disclosure, a shape of the openingincluded in the shielding layer of the sensing pixel areas does not haveparticular limitations as long as an aperture of the opening increasesalong a predetermined direction from a corresponded pixel center. Forexample in FIG. 6A, an aperture of the first opening O₁ exponentiallyincreases along a first direction (e.g. the X direction) from a centerof the first pixel P₁. It is appreciated that as the second opening O₂is mirror symmetrical to the first opening O₁ along the first direction,an aperture of the second opening O₂ exponentially increases along aninverse of the first direction (e.g. the −X direction) from a center ofthe second pixel P₂. Furthermore, when the sensing pixel area includesfour sensing pixels as shown in FIG. 6B, an aperture of the thirdopening O₃ exponentially increases along a second direction (e.g. the Ydirection) from a center of the third pixel P₃, and an aperture of thefourth opening O₄ exponentially increases along an inverse of the seconddirection (e.g. the −Y direction) from a center of the fourth pixel P₄.

In one embodiment, a shape of the first opening O₁, the second openingO₂, the third opening O₃ and the fourth opening O₄ is a semicircle asshown in FIGS. 7A and 7B.

In one embodiment, a shape of the first opening O₁, the second openingO₂, the third opening O₃ and the fourth opening O₄ is a trapezoid asshown in FIGS. 8A and 8B.

In the present disclosure, each of the sensing pixel areas As (e.g.including the first pixel P₁, the second pixel P₂, the third pixel P₃and the fourth pixel P₄) is the light sensing pixel manufacturedindependently or light sensing pixels adjacent or non adjacent to eachother in a same pixel matrix without particular limitations. In someembodiments, a part of pixels in a pixel matrix are selected as thesensing pixel areas As and the other pixels of the pixel matrix performother functions.

For example referring to FIG. 9, a sensing element includes three typesof sensing pixels including red pixels (R), green pixels (G) and bluepixels (B) is shown. A part of the G pixels are respectively disposedwith a shielding layer and a micro lens thereupon, wherein the shieldinglayer includes an opening (e.g. triangular first opening O₁ and secondopening O₂ in the first embodiment of the present disclosure). The otherpart of the G pixels, the R pixels and the B pixels are not disposedwith the shielding layer and the micro lens thereupon. In this case, thepart of the G pixels are used to capture the image frame containinginformation of object depth, and the other pixels are used to capturethe image frame containing information of two-dimensional image.

In addition, the optical distance measurement system 1 of the presentdisclosure is able to estimate the position of the object 9 using a fewsensing pixels (e.g. the first pixel P₁ and the second pixel P₂). Inother words, if the optical distance measurement system 1 of the presentdisclosure includes a large number of sensing pixels, e.g. a sensingpixel matrix including 300×300, 600×600 or 900×900 pixels, more positioninformation of the object 9 is obtainable to be used to construct athree dimensional image of the object 9.

It should be mentioned that values in the above embodiments, e.g. theprojective distances and different values, are only intended toillustrate but not to limit the present disclosure.

As mentioned above, the conventional distance measurement system and thegesture recognition system need a higher cost and size, and generally anadditional light source is required. Therefore, the present disclosureprovides a sensing element and an optical distance measurement system(FIG. 1) that capture images with mirror symmetrical sensing pixels toperform the phase detection so as to identify the two-dimensionalposition, the three-dimensional position and the position variation ofan object, and have the advantages of low cost and small size since alight source is not required.

Although the disclosure has been explained in relation to its preferredembodiment, it is not used to limit the disclosure. It is to beunderstood that many other possible modifications and variations can bemade by those skilled in the art without departing from the spirit andscope of the disclosure as hereinafter claimed.

What is claimed is:
 1. A sensing element, comprising: a plurality ofsensing pixel areas, wherein each of the sensing pixel areas comprises:a first pixel; a second pixel adjacent to the first pixel; a firstshielding layer disposed upon the first pixel and having a firstopening, wherein an aperture of the first opening increases along apredetermined direction from a center of the first pixel; a secondshielding layer disposed upon the second pixel and having a secondopening, wherein a shape of the second opening is mirror symmetrical tothat of the first opening along the predetermined direction; and atleast one micro lens disposed upon the first shielding layer and thesecond shield layer, wherein the first pixel and the second pixelrespectively receive incident light beams of different phases, and ashape of each of the first opening and the second opening is a triangle,and a corner of the triangle is respectively at the center of the firstpixel and a center of the second pixel.
 2. The sensing element asclaimed in claim 1, wherein the first shielding layer and the secondshielding layer are directly coated on or laid over the first pixel andthe second pixel, respectively.
 3. The sensing element as claimed inclaim 1, wherein an area of the first opening is 5 to 45 percent of thatof the first pixel.
 4. The sensing element as claimed in claim 1,wherein the aperture of the first opening exponentially increases alongthe predetermined direction from the center of the first pixel.
 5. Thesensing element as claimed in claim 1, wherein the first pixel and thesecond pixel are respectively aligned with one micro lens.
 6. Thesensing element as claimed in claim 1, wherein a part of the first pixeland a part of the second pixel are covered by a same micro lens.
 7. Thesensing element as claimed in claim 1, wherein a first area summation ofthe first shielding layer and the first opening is larger than an areaof the first pixel, and a second area summation of the second shieldinglayer and the second opening is large than an area of the second pixel.8. The sensing element as claimed in claim 1, wherein the firstshielding layer and the second shielding layer are selected from twometal layers in the CMOS manufacturing process.
 9. The sensing elementas claimed in claim 1, wherein the second pixel is a diagonal pixel ofthe first pixel.
 10. An optical distance measurement system, comprising:a lens; a sensing element configured to sense light penetrating the lensand output an image frame, and comprising a plurality of sensing pixelareas, wherein each of the sensing pixel areas comprises: a first pixeland a second pixel; a first shielding layer disposed upon the firstpixel and having a first opening, wherein an aperture of the firstopening increases along a first direction from a center of the firstpixel; a second shielding layer disposed upon the second pixel andhaving a second opening, wherein an aperture of the second openingincreases along an inverse direction of the first direction from acenter of the second pixel; and at least one micro lens disposed betweenthe lens and the first shielding layer as well as the second shieldinglayer; and a processing unit configured to generate, according to theimage frame, a first subframe corresponding to the first pixels and asecond subframe corresponding to the second pixels, and estimate aplurality of distances of different positions, according to the firstsubframe and the second subframe, on a surface of an object to obtain athree-dimensional image of the object.
 11. The optical distancemeasurement system as claimed in claim 10, wherein each of the sensingpixel areas comprises one micro lens which is aligned with both of thefirst opening and the second opening.
 12. The optical distancemeasurement system as claimed in claim 10, wherein each of the sensingpixel areas comprises two micro lenses each being aligned with one ofthe first opening and the second opening.
 13. The optical distancemeasurement system as claimed in claim 10, wherein the first shieldinglayer and the second shielding layer are respectively coated on or laidover the first pixel and the second pixel.
 14. The optical distancemeasurement system as claimed in claim 10, wherein an area of the firstopening is 5 to 45 percent of that of the first pixel.
 15. The opticaldistance measurement system as claimed in claim 10, wherein a shape ofthe first opening and the second opening is a triangle, a trapezoid or asemicircle.
 16. The optical distance measurement system as claimed inclaim 10, wherein the aperture of the first opening exponentiallyincreases along the first direction from the center of the first pixel,and the aperture of the second opening exponentially increases along theinverse direction of the first direction from the center of the secondpixel.
 17. The optical distance measurement system as claimed in claim10, wherein the processing unit is further configured to calculate afirst projective distance from a first imaging position to a firstreference line in the first subframe corresponding to each of thesensing pixel areas, calculate a second projective distance from asecond imaging position to a second reference line in the secondsubframe corresponding to each of the sensing pixel areas, and estimatethe plurality of distances according to a difference value of the firstprojective distance and the second projective distance corresponding toeach of the sensing pixel areas.
 18. The optical distance measurementsystem as claimed in claim 10, wherein each of the sensing pixel areasfurther comprises: a third pixel and a fourth pixel; a third shieldinglayer disposed upon the third pixel and having a third opening, whereinan aperture of the third opening increases along a second direction froma center of the third pixel; and a fourth shielding layer disposed uponthe fourth pixel and having a fourth opening, wherein an aperture of thefourth opening increases along an inverse direction of the seconddirection from a center of the fourth pixel, wherein the processing unitis further configured to generate, according to the image frame, a thirdsubframe corresponding to the third pixels and a fourth subframecorresponding to the fourth pixels.
 19. The optical distance measurementsystem as claimed in claim 18, wherein the second pixel is a diagonalpixel of the first pixel, and the third pixel is a diagonal pixel of thefourth pixel.